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Welding Titanium Question

09-06-2013, 10:02 AM

Hey everyone,

New here, but Ive done a good amount of searching around I still have a question.
I've been welding Chromoly and aluminum for about 3 yrs, self taught and i have had the opportunity to learn to weld Ti at work. i purchased a large gas lens set up and a #15 cup and I made some purge plugs and am back purging the weld area. The weld color is acceptable from what i understand (silver/straw) but i am getting slight discoloration away from the weld bead area (see picture) is this okay? or is this just as bad as discoloration in the weld? If its bad any possible solutions you can recommend? Thanks!

Comment

So weld in shorter spurts, tighten up puddle spacing, and i'm not using near all the 80 amps its just what the machine was set at but ill turn it down anyhow. Thanks for the responses so far if anyone has any other input the more the merrier!!

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As a self taught welder you have probably tried different techniques. As with any other material choose wisely the type and thickness of the filler metal. As for the cup...well...thin wall like the .035 would be better suited with the cup size and type your using. If you get the chance to weld thicker parts, like .250 to 1.0 I would suggest ditching the gas lense and shoot with a straight 8
The material has a low rate of thermal conductivity. The thicker, the easier. With the thinner parts like the tubing in your pic remember that the filler metal has a tremendous impact on the overall heat input of that part.
In other words, the more filler, the more heat. Remember that Ti and Argon have an affinity for one another. But all good things in moderation.
The last point I will make is to watch "the glow" in the puddle. At a certain point the glow or brightness dissipates and its time to move, don't soak the puddle too long, and try not to move too slow and compensate with widely spaced beads.
In my opinion Ti is easier to weld than stainless steel. But dirty aluminum is the mother of all evil.

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Wow! Lots of great info here!! Thanks! I can't wait to get back at it next week, so just to clarify though, if done proper I shouldn't see the discoloration outside of the weld area? How much does it effect the material? I want these and all of my Ti welds to be on point when we start sending product out the door. Also I think the filler rod was 1/16 but I'd have to check when I get back to work.

As a self taught welder you have probably tried different techniques. As with any other material choose wisely the type and thickness of the filler metal. As for the cup...well...thin wall like the .035 would be better suited with the cup size and type your using. If you get the chance to weld thicker parts, like .250 to 1.0 I would suggest ditching the gas lense and shoot with a straight 8
The material has a low rate of thermal conductivity. The thicker, the easier. With the thinner parts like the tubing in your pic remember that the filler metal has a tremendous impact on the overall heat input of that part.
In other words, the more filler, the more heat. Remember that Ti and Argon have an affinity for one another. But all good things in moderation.
The last point I will make is to watch "the glow" in the puddle. At a certain point the glow or brightness dissipates and its time to move, don't soak the puddle too long, and try not to move too slow and compensate with widely spaced beads.
In my opinion Ti is easier to weld than stainless steel. But dirty aluminum is the mother of all evil.

Comment

As far as an "acceptable" weld on Ti, that is entirely up to the manufacturing engineer or the customers specs. Unlike other materials titaniums welding requirements are industry specific. Normally the procedures are developed by the engineers that design the parts themselves.
My first experience with this type of material was in Aerospace. Color is the primary determining factor of how well the welding process was performed.
You mentioned "straw" coloration. This would have been rejected. Nitric Acid etching would remove a specific amount of material and the process would be repeated.
Look online for the "color schedules" that some companies refer to as a guide. I believe most welding procedures as well as the procedures for the "removal" of the color varies.
Your welds should be just fine. Coloration forms when the weld and the surrounding material is getting too much atmosphere before it reaches a low enough temperature not to oxidize. In other words, its the same challenge as getting "color" on stainless but in this case, "no color" is the goal.
Removal of the unwanted color is all you really have to do to ensure the best weld quality. If you see blue or purple its not the end of the world. Just stay away from grey or brown. I've even seen white, that was on thicker material however. But mechanically removing the oxide is normal. Wire brushing can be good/ok. Just use quality brushes that are clean and aren't too warn out. A stray wire in the weld puddle will get annoying.
Sand blasting and etching are the best ways to remove discoloration from the surface.
As far as achieving good color, Ti doesn't seem to wet in like other ferrous materials. To me, it behaves more like Al. So be aware of soaking too long and roll back of the throttle as you "drop" the temp as you move forward with the arc, not the puddle. Its minute but if Im making any sense you'll see this under the hood. Faster and steadier. Good luck.

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I like to create a purge dam with aluminum foil behind the area I'm welding. It helps hold the argon a bit longer. This is 1 1/4" OD x 0.035" tubing. You can see some light straw on this joint. I'm not too happy if I see blue. If I'm seeing blue where it is in your photo, it says to me that I am moving too slowly and the whole area is getting too hot. I like using 0.035" or 0.040" wire. One tip I can offer is to anticipate where your purge will get blocked by the bead. In other words, as you feed filler and the bead raises up a bit, you can get some turbulence behind the bead if your torch angle is a bit low. The bead blocks the argon. So I try to keep my torch angle at 85 to nearly 90 degrees to the joint. And as others have said, try to tighten up your dip spacing. I also suggest to practice on steel to save some money. Use your same gas lens and cup. If you can weld steel without color, you can get a lot closer to welding titanium without much color beyond light straw. Hope that helps a bit.